From Earth Science On-Site
Knowle Quarry, Shropshire
KEY STAGE 4 TEACHING TRAIL: SITE 2
© GeoconservationUK ESO-S Project, 2013
It is anticipated that the ideas and materials presented here will be adapted by schools, and others, to be more appropriate for their own purposes and programmes of study.
In such circumstances please acknowledge the source as the Earth Science On-Site project.
Site 2: Ape Dale and Wenlock Edge
Return to the coach and travel south along the A4169 to the junction with the A458. Turn right onto the A458 and within 500 metres turn left onto the B4371. After 2.25 km the site office of Bardon Aggregate is on the right. A further 1.5 km along the B4271, just before the right turn to Hughley, the Wenlock Edge (Presthope) car park is on the right. This is big enough for a coach, although it is a very tight fit. Do not block the gate to the track from the car park onto Wenlock Edge when parking here.
Figure 2: Map of the Knowle Quarry sites
Warn the group that sensible behaviour is required on the footpaths which are along the top of Wenlock Edge, and also become slippery when wet. Lead the group uphill out of the car park and then north eastwards along the footpath on the crest of the scarp slope of Wenlock Edge. After a hundred metres or so the view point to Shrewsbury in the NW is revealed where the trees have been cut back. The landscape here is classic scarp and vale topography, heavily influenced by the geology of dipping, alternating more and less resistant rocks. The first task is to orientate the group and get them thinking about the landscape.
Figure 3: Section across Wenlock Edge
Figure 4: Site 2: Presthope view point
|Suitable questions at this site
|Ask the group to use a compass to establish which direction they are facing.
|Using the section on worksheet 3 ask the group in which direction the beds are dipping?
||To the east.
|Ask the group to predict what kinds of rock lie below Wenlock Edge.
||The beds are layered, a good indicator of sedimentary rocks.
|Ask the group to use The Principle Of Superposition to work out in which direction the younger beds lie.
||To the east (i.e. in the direction of dip in rocks that are not overturned.).
|Ask the name of the ridge on which they are standing.
|Ask the group the name of the valley in front of them.
|Ask the group to explain why the land in the valley is lower than on the ridge.
||Hills are formed by more resistant rocks, whilst less resistant rocks are eroded to lower levels. Ape Dale runs north–south along a less resistant bed of shales.
|Ask the group why Ape Dale has a steeper side and a more gently sloping side.
||The western slope is the dip slope of the beds below, whilst the steeper eastern slope is undercut into softer shales protected on top by more resistant rocks.
|Summarise the predictions the group have made about the rocks beneath their feet. They are sedimentary, they are dipping eastwards, and they are more resistant to weathering.
Those groups who have previously completed the Earth Science On-Site site at The Ercall may want to extend this part of the visit by placing the two sites in a geological context.
|Suitable questions at this site
|What age were the rocks we saw at the Ercall?
||(Precambrian volcanics) and Cambrian sandstones.
|Using the section on the worksheet are the beds here older or younger than the beds at the Ercall?
||Younger (because they are on top – The Principle of Superposition). These are Silurian in age, about 420 million years as opposed to the 540 million years of the sandstones at The Ercall.
|What do you notice about the beds between the Cambrian and the Silurian?
||They are all marine beds, with periods of erosion (called unconformities). This area was a shelf sea on the edge of an oceanic area to the north west. No continental deposits are formed here till the Devonian period. See the earth science briefing for details).
|Point out that the 130 million year gap between the two sites is represented here by the thickness of rocks between Wenlock Edge and outcrops to the west like The Lawley.